Bis (N,N-dialkylaminoalkyl) ethers of the formula (R.sub.2 NR').sub.2 O, in which R is a methyl or ethyl group and R' is ethyl or propyl, are useful in the production of polyurethanes, especially polyurethane foams. One member of this family of compounds--bis (N,N-dimethylaminoethyl) ether (BDMAEE)--is an industry-standard polyurethane catalyst. It is primarily used to catalyze the blowing reaction, i.e., the reaction of isocyanate and water to produce CO.sub.2, in the production of flexible polyurethane foam.
The are several known processes for producing bis (N,N-dialkylaminoalkyl) ethers, including BDMAEE. For example:
U.S. Pat. No. 4,177,212 (Poppelsdorf, 1979) discloses a two-step, one pot reaction for producing bis (N,N-dialkylamino)alkyl ethers in which sodio N,N-dialkylaminoalkoxide is reacted with a sulfur oxychloro-containing compound selected from sulfuryl chloride, thionyl choride or chlorosulfonic acid, in the presence of an organic diluent/dispersant and an N,N-dialkylaminoalkanol. The intermediate reaction product is heated to an elevated temperature to produce the bis (N,N-dialkylamino)alkyl ether. This process has disadvantages including disposal problems associated with by-product salt and special handling required for the chloro-containing compound.
U.S. Pat. No. 4,247,482 (Poppelsdorf, 1981) discloses a process similar to the process described in U.S. Pat. No. 4,177,212 except that SO.sub.3 vapor is used in place of the sulfur oxychloro-containing compound. Besides the problems associated with isolation and disposal of the by-product sodium sulfate, an additional disadvantage of this process is the problems associated with handling the toxic and corrosive SO.sub.3.
U.S. Pat. No. 4,474,988 (Kaiser, 1984) discloses production of bis (N,N-dialkylamino)alkyl ethers by reacting (N,N-dialkylamino)alkanol over a heterogeneous solid acid catalyst. This process has the drawback of producing several by-products due to low selectivity.
U.S. Pat. No. 5,214,142 (King, 1993) discloses a process for preparing bis[2-(N,N-dialkylamino)alkyl]ethers by contacting a carboxylated aminoether with a metal oxide catalyst. The aminoethers are prepared by contacting an active hydrogen-containing compound, such as an alcohol, with a carbon dioxide synthon in the presence of a metal oxide catalyst.
The use of basic zeolites in the dehydrative etherification of alcohols is known in the art. For example, Ziolek, et al. (Catalysis Letters, Vol. 37, pages 223-227, 1996) disclose the preparation of dimethyl ether from the reaction of methanol in the presence of NaY zeolite. Barrault, et al. (In Catalysis of Organic Reactions, edited by Frank Herkes, pages 13-23, Dekker, 1998) report the etherification of glycerol to di- and triglycerols in the presence of basic zeolite catalysts, including sodium, potassium, and cesium exchanged Y zeolite. However, there are no known references to etherification of alcohols containing amine functionality using a basic zeolite catalyst.